Im CUTTING #121 - Monrovia, CA
 

Hi Guys,

Been reading alot of the forums sure do like the MM. Rather make things myself than buy them. Usually costs me though. Just completed an addition on the house that ate 5 years:o. In return I get a new garage:).

I'm finishing the drywall on the garage and dreaming:rolleyes:. That's what got me to your site. Been a woodworker for many years and wanted to start making wooden clocks. Not wanting to become a gear cutting expert I figured a CNC machine was the way to go.

The MM looks like a good project toward my goal. Maybe I can get it finished before I retire. Then I can make stuff to help me eat.

Looks like a good organized work group. Hope I can add something.

Thanks, John

Welcome John!

Heath,

Thanks for the welcome :)

How do I contact some one to get the laser parts? I sent a PM last week to Joe but got no response. Not sure if he is still doing that.

I would like to get started collecting the drive system and electronics parts.

From what I read I think that the belt drive is for me. Has anyone put a laser on the MM? A router is plenty for me now but in the future I'm sure Lasers will become affordable.

I also came across an Excel file with all of the current builders. Can't find it now. I'm looking for some one in my area that may be working on or interested in a MM.

John

Found MetalHead's Thread for the laser parts

John,

Look at this for the builders list.

http://www.mechmate.com/forums/showthread.php?t=1210

People have a laser on their machine. What application are you thinking of using a laser?

Nils,

Thanks for the builders list.

Laser cutting in wood, engraving that sort of thing. Not sure about the size of the Laser. Once you get the laser then the experimenting starts.

Just wanted to make sure that what I build will not prevent me from going to this in the future.

You could easily mod the MM for many different tool heads.

The tool platform looks to have plenty of room to adapt tools.

Referencing the use of a laser in the future. A thought on a performance test would be to install a pencil and see how repeatable the drives and carriages are. Drawing plus signs in the 4 corners of the table over and over again would be a way of checking for wear on the machine.

Has any one tried drawing a full size pattern then repeating it and check the drift/offset in line spacing.

A laser does not have the side load a router has so holding torque of the opposite axis isn't stressed but I would think that the overall looseness of the machine will accumulate.

My only overall concern about the build is that I don't understand the software used and how it is interfaced yet but that just takes reading.

My fear is those all night sessions of trying to make it play with the hardware.

John

The only looseness in the machine would be a backlash type effect and from a previous thread, backlash does not accumulate. It is only +\- the backlash value. Look at some of the projects being done here and you will see the accuracy repeatability is there.

So the machine is laser capable as it is except for maybe doing the belt drive change to eliminate the backlash.

I'm setting up with Mike to order the Laser and machined parts.

I next need to get my electronics. I just need to read the threads to pick the motor/belt drive setup to use.

That would leave us without much fun without those night session :D

At least on this site someone in the world will be awake to talk it over with.:)

Lol :)

Motor and Electronics decisions?
 

Ordered my laser parts from Metalhead and they will be here this Friday.

Time to start on my next quest: Motors and Electronics

I am in the process of deciding on the Motors and Electronics for my build.
I am planning on a 3:1 beltdrive so I will be purchasing direct drive motors.
The choice for motors is the Keling KL34H280-45-8A. In stock $89 USD. Price is the main driver for this choice and I am interested in any information on limitations or problems with this motor. You get what you pay for. The difference between $207 (4-$828) for the OM vs $89 (4-$356) for the Keling is substantial.

Per another thread:
“The KL34H280-45-8A motor has 2.2mH inductance when wired either half-coil or bipolar parallel. It can be used with power supplies up to 47VDC, 25 amps would allow full speed under all conditions.” “I would use a 35VDC to 40VDC power supply”

PMDX-122-Bundle4 >> Bi-Directional Breakout Board bundled with 4 each Gecko G203V ($637). Seems to be the standard setup.

PMDX-135-5020 >> Power Prep Module, 50 volt, 20 ampere ($107)

Avel Y236907 800VA 45V+45V Toroidal Transformer ($105)

Total cost estimate: $1205

John

John, that transformer voltage seems a touch high for your design target; 45VAC * 1.42 = 63.9 VDC. If you want 40VDC, you need a 28VAC transformer. For 45VDC, something around 32VAC.

I usually double check specifications against the G540 solution which worked for me. The motors you have chosen are out of range for that; but the 640Oz/In seems a little more than you need if you're going to belt reduce it. Somebody else should double check me, but it seems that you could use the KL34H260-60-4AB at 465 Oz/In and still have oodles of torque. That would allow the G540, which will save you some more $$. Of course, this probably won't work for direct drive, so you need to go to belt drive right away.

Brad, thanks for the transformer calc and info.

I want to go with a proven design but also want to save cost. On my first build I don't want experiment too much.

The KL34H260-60-4AB draws 6amps vs the 280's 4.5 amps. I need to read more on the two motors and the G540 to see. Also read a thread about the DB9 connector and current draw through the small pins. Could remove the connectors and hardwire to terminal blocks. Probably won't do much for the warranty of the G540.

I would like to hear from someone that has used the setup successfully. Don't want to save too much money only to throw it away later.

I raise the since you said "also want to save cost." the transformer can be smaller, report of 300VA is sufficient.

John, this thread may help you: Soldering DB9 connectors on the motor cables for the Gecko G540 I havn't seen reports of the mating pins failing yet.

or these ribbon cable DB plug?
Attachment 8513

Okay, I can handle the soldering of the DB9 connectors.

Are we all okay with the KL34H260-60-4AB and G540 on a 3:1 belt drive??

The KL34H260-06-4A does not show data for Half-Coil or Bipolar like the Oriental Motors. What mode is the data describing? Is this the limitation of the cheaper motor? Or am I missing something. Does it matter?

John, I just looked at the inductance and torque numbers quickly when pointing out that motor as a possibility; I'll try to do a full workup on that motor later (I don't trust or believe the published amp or volt numbers on stepper motors in general). You will likely want to run it half coil. However, another good source of an answer would be a quick email to Geckodrive, asking them which of the KL34H motors is a reasonable match.

Good Idea, I'll call Gecko this morning, Thanks.

I appreciate the help from all of you. I don't want to be lazy and have you do the work for me but I also don't want to be come a stepper motor expert either.

Found some good wiring diagrams at Keling

http://www.kelinginc.net/G540WD.pdf

Don't worry John, by the end of the build, you will be a stepper motor expert.... like it or not :)

I called Gecko and the bottom line is that you compare the motor specs to the drive specs. The G540 is 4 G250's in a package. The motor current must be less than 3.5 amps. :(

I've think I have just possibily, maybe decided to go with the G203V since it is effectively bullet proof and well known.:confused:

Gecko did give me motor sources to check out other that Oriental or Keling. They were new to me.

http://www.camtronics-cnc.com/stepper-motors.asp

http://www.homeshopcnc.com/RSstepperMotors2.html

In between Keling and Oriental on pricing.:rolleyes:

One thing is for sure if you stick to the plans it will work and will be easier for us to help troubleshoot issues in the future!!!

3:1 belt drive
KL34H260-42-8A
Motor 400in/oz
Pinion 1200 in/oz

mH Max V VAC PS
Bipolar Parallel 1.65 41 34.9
Bipolar Series 6.6 82 69.9

Is there an advantage of one over the other?

Okay, just to back up my ramblings above:

I have PK296A2A-SG7.2 motors running just fine with the G540 wired half-coil.

From OM, the PK296A2A-SG7.2 specs are:
Torque 44 Lb/In = 704 oz/in
Rotor Inertia 7.7 oz/in
Step Angle 0.25 degrees
Max Speed 250 rpm

With two wiring choices (U)nipolar or Bipolar (S)eries:
U: 2.1A 1.4V 0.48ohm 1.5mH 704oz/in
S: 3.0A 2.0V 0.96ohm 6.0mH 704oz/in

This happens to directly correspond to the PK296-F4.5A motor, which provides these numbers:

U: 4.5A 2.0V 0.48ohm 1.5mH 310oz/in
S: 3.18A 2.8V 0.96ohm 6.0mH 440oz/in
P: 6.3A 1.4V 0.24ohm 1.5mH 440oz/in
and we can intuit:
H: 4.5A 2.0V 0.48ohm 1.5mH 310oz/in

Where P = Bipolar ℗arallel and H = Bipolar (H)alf coil

See the rules here: http://www.probotix.com/stepper_moto...polar_bipolar/

I'm asserting these two motors are the same, however, note that the gearbox limits the torque to 704 oz/in; you could drive the motor harder, but OM doesn't want you to. If you did drive the motor at full amperage, you would have hypothetical torque of 310 * 7.2 = 2232 oz/in or 440 * 7.2 = 3168 oz/in. And probably shaved gears.

So the difference in the amperage specs have everything to do with keeping you in the torque range for the gearboxes. The resistance and inductance specs match, meaning the windings are the same.

Okay, so now we move on to looking at the Keling motors, trying to find one that has roughly the same winding specs as the OM motor. Note that we may not run it up to it's full amperage; that's okay, as long as we end up with enough torque after you gear it down.

I missed the fact that the original motor I pointed to was 4 wire. We need a 6 or 8 wire motor.

Keling says KL34H260-60-4A: (But it's 4 wire only, so can't half coil. no go).
P: 6.0A 1.74V 0.29ohm 1.7mH 465oz/in

KLH34H260-42-8A: (8 wire, good match)
P: 6.0A 1.6V 0.27ohm 1.65mH 400oz/in
S: 3.0A ?3.2V 1.08ohm 6.6mH 400oz/in
U: 4.2A ?2.7V 0.54ohm 1.65mH 282oz/in
intuit:
H: 4.2A ?2.7V 0.54ohm 1.65mH 282oz/in

But we're going to cap off at the max amperage of the G540: 3.5A. Let's say that gives us around 200oz/in (I HAVE NOT VALIDATED THIS ASSUMPTION WITH A CALCULATION OR MEASUREMENT). That places you at 600oz/in at the pinion.

So, it's very close to provably working, but if you want a sure thing, you'll need different motors, or the bigger drivers.

The Camtronics 34H260-42-8B sure looks suspiciously like the Keling. However, the 34H260-60-8B 465oz looks like the 4 wire Keling with 8 wires, which would match up a little better and give a dozen or two more oz/in.

The HomeShopCNC motors all seem to be too big, and 4 wire only.

John, you may very well want to go with the proven path and the 203Vs, I just wanted to complete the thought process for the record.

Brad,

Your explaination and the link to the rules closed up all the gaps I had in understanding what is going on (for now).

On this build I have decided to go with the tried and true.

Thanks, John

KL34H260-60-4A

32 X SQRT(inductance) for lowest voltage

Start here
http://www.mechmate.com/forums/showt...96&postcount=7


Ok I got some reading to do.

I know the first motor above has been used in a belt drive setup.


But what is the difference in it and this one?

KLH34H260-42-8A

I am with Gerald on not derating the motors. I think either of these motors will be fine running at 48 VDC

Thoughts?